Although momentum is growing in the development and manufacture of electric vehicles, the success of such vehicles in everyday use will continue to be limited if there is no substantial improvement in their range of travel. Current battery technology used in electric vehicles limits the range of the vehicles, thus requiring frequent stops for recharging. Due to the time and effort required to recharge the batteries of an electric vehicle and the limited driving distance of such vehicles on a single charge, there is a need to extend the run time of electric vehicle batteries and to use battery power more efficiently.
Some solutions have been proposed in recent years, but they are lacking for various reasons. For example, US Patent Publication No. 2010/0184560A1 describes a system that incorporates two battery banks with a switching network that switches between the two banks for alternate charging and discharging. This system requires a separate drive motor/alternator set for each bank of batteries, which means two drive motor/alternator sets are needed to recharge the two battery banks. This requirement is a significant disadvantage as it adds more weight to the vehicle, and therefore decreases overall efficiency.
U.S. Pat. No. 6,734,645 describes an electric automobile that includes one or more free-turning wheels which each drive a generator via a gearbox. The generator charges one of a pair of battery packs while the other non-charging battery pack powers an electric motor that turns a pair of wheels through a differential. When the battery pack powering the electric motor nears depletion, a switching network switches in the generator to charge the depleted battery and switches in the charged battery to power the electric motor. Driving a generator through a gearbox attached to a vehicle's wheel as described in this patent is an inefficient way to generate electrical power to recharge vehicle batteries.
What is needed is a system for recharging one battery pack while another battery pack powers the vehicle, which efficiently switches between the depleted and charged battery packs, and which adds no unnecessary weight to the vehicle.